Adherence to prophylactic medications is crucial if HIV-infected patients are to avoid preventable opportunistic infections. As well, it is critical if patients are to benefit from the protease inhibitors and other new antiretroviral medications. Currently very little is known about medication adherence among HIV-infected patients. However, in a recent study, patients report missing 30-40% of their medication doses. Our patients show considerable lack of understanding of their medication regimen and the importance of their prophylactic medications. The literature supports that education can enhance adherence rates, and use of an information-intensive interviewing style can increase clinicians' identification of adherence problems. Our clinical trial employs an information-intensive interview to increase the clinic staff's awareness of adherence problems among intervention patients and to provide education for patients who lack understanding of their medications. To date, there are no reported studies to determine that interventions effectively increase adherence in HIV-infected patients. We will address this gap in knowledge through our randomized, controlled intervention trial to improve adherence among our HIV-infected patients. The hypothesis of this trial is that medication adherence can be improved in our patient population by improving patients' knowledge of their medical regimen. In our randomized clinical trial, patients assigned to the intervention group are administered a structured interview to ascertain patterns of medication taking and knowledge of medications and disease. These patients receive individualized education regarding their medication regimen and are taught tailoring, how to better incorporate their medication taking into their daily routine. For all patients, medications adherence, the primary outcome of the study, is quantitated using Medication Event Monitoring System (MEMS) devices, bottle caps that record the date and time that the bottle is opened. During the study all patients use a MEMS device on the bottle containing their PCP prophylaxis. Pill counts are obtained at each visit to validate the MEMS data. The secondary study outcome, improved patient knowledge of medication and disease, is assessed through a questionnaire conducted on the first and last exit interview. Study enrollment began June 12, 1996, and 84 patients are enrolled to date. Approximately 25 patients have completed the six month study period. The mean adherence rate is 75% of daily doses taken, with a range of 7% to 97% daily adherence. We have not yet compared adherence rates between the intervention and control arms.